Method and apparatus for producing flame jet and controlling temperature and flame stability of same



ame M, wm@ J. A. BROWNING 3,255,802

AND APPARATUS FOR PRODUCING FLAME JET AND CONTROLLING m' n I TEMPERATUREAND FLAME STABILITY OF' SAME fue@ cept. 5, 1965 5 Sheets-.Sheet l METIvOD Hrs.

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METHOD AND APPARATUS FOR PRODUCING FLAME JET AND CONTROLLING TEMPERATUREAND FLAME STABILITY OF SAME Filed Sept. 5, 1963 .'5 Sheets-Sheet 2 doxYGr-:N FUEL |50- u. l t 0 S looui :n

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Umted States Patent O 3,255,802 MIETHD AND APPARATUS FR PRUDlUCING FLAMEJET AND CONTRLLING TEMPERA- IPURE AND FLAME SCF-ABILITY F SAME dames A.Browning, Hanover, NH., assignor to H. E. Fletcher Co., West Chelmsford,Mass., a corporation of Massachusetts Filed Sept. 5, 1963, Ser. No.306,887 7 Claims. (Cl. 158-4) The present invention is acontinuation-impart of my copending application Ser. No. 666,680, filedlune 19, 1957, now Patent No. 3,103,251, granted Sept. 10i, 1953.

This invention relates to a method and apparatus for burning a fuel toyform a flame jet and, more particularly, the invention is concernedwith a method of producing a cooled liame jet wherein oxygen and aninert gas such as nitrogen are mixed with a liquid fuel and the fuel isburned at superatmospheric pressure in a confined combustion chamber toprovide a relatively high velocity stream of products of combustionwhose temperatures and liame stability may be varied in accordance witha controlled use of the inert gas component in lthe combustion chamber.

As disclosed in the above application, I have determined that a nitrogencooled flame jet, as distinct from an oxyfuel flame jet in-Which pureoxygen is used as the oxidant, is capable of providing much lower flametemperatures than those possible with a conventional oxy-fuel jet. Inthis connection it has been found that use of a water coolant for `theburner combustion chamber may be eliminated since appreciable amounts of`thermal energy is absorbed by the inert nitrogen. In addition, thenitrogen cooled flame is found to provide for improved removal ofspallable mineral bodies in carry-ing out channelling and other mineralWorking operations.

However, in producing a nitrogen cooled type llame jet in which theinert gas component occurs in an appreciable amount, various problemsare encountered. For example, it is necessary to maintain the percentfuel introduced within definite limits which are neither too rich or toolean to support combustion. Flame stabilization of a nitrogen cooledtype flame jet must be accomplished within much narrower stabilitylimits than is the case with a pure oxygen-fuel jet. The region definedby these limits in any given instance may be conveniently referred to asthe region of stable burning of a flame jet. Other factors whichdetermine such a limiting region of stable burning are stream velocityand size of combustion charnber employed.

It is a chief object of the present invention, therefore, to provide animproved method and means for producing a ,cooled llame jet such as thenitrogen cooled flame jet above-noted.

Another object of the invention is to provide an improved method andmeans for supplying and burning fuel in a combustion chamber in which acontrolled quantity of inert gas may be constantly introduced. It is afurther object of the invention to devise a burner construction in whichstable burning may be realized with relatively small burner sizes toprovide a c-ooled flame jet.

These general objectives may, I find, be realized by controlling theintroduction of fuel and inert gas into a combustion chamber in apredetermined manner and also by controlling the movement of products ofcombustion which are produced within the combustion chamber.

I have determined that I may control the introduction of fuel`advantageously by employing an elongated mixing space in which fuel,oxidant and inert gas are premixed at a temperature below that at whichthe fuel vaporizes and the mixture is then led into a combustionchamber. In this way I may utilize-a liquid fuel such as kerosene andform a dispersion of relatively coarse fuel droplets. I further providefor the premixing space communicating with the combustion chamberthrough a special liame stabilizing section of the burner. By means ofthis arrangement I am enabled to provide for the liquid fuel droplets,oxidant and inert gas being brought together to produce a combustiblemixture in which the coarse droplets are homogeneously distributed andyet the liquid fuel droplets occur in varying sizes and may burn forvarying intervals of time.

I have further discovered that this combustible mixture containing arelatively large amount of inert gas may be burned in the combustionchamber to provide products of combustion whose movement and burningcharacteristics can be controlled in a highly unusual and novel manner.This discovery is based on a recognition of the fact that the reactantshave a velocity of llame propagation in the combustion chamber which islimited by the nitrogen component in a significant degree.

Specifically, I find that by burning relatively coarse fuel dropletsinterspersed with liner droplets, in an environment in which thevelocity of llame propagation is limited by a nitrogen component, and byproviding a combustion chamber having predetermined physicalcharacteristics, including a flame stabilizing surface through which thedroplets are injected, it becomes possible to induce a recirculation 'ofproducts of combustion at the liame stabilizing surface. By thusinducing `a recirculation of the products of combustion at the lpointwhere incoming droplets pass into the combustion chamber, I provide fora continuous igniting action on incoming reactants from the prernixingchamber. The recirculated portion of the products of combustion havebeen visually observed and are seen to become distributed in the shapeof a torus located all the way around the fuel inlet in the llamestabilizing surface of the burner through which the mixture is injected.This igniting action makes possible operation of the llame jet usingquantities of fuel on both the lean s-ide and the rich side to an extentnot heretofore realized. It will be apparent therefore that for anygiven set of operating conditions an improved temperature control mayberealized and the region of stable burning may be extended and morelatitude is possible in the size of the combustion chamber which may beemployed.

The nature of the invention and its other lobjects and novel featureswill be more fully disclosed from the following description of thepreferred embodiments of the invention shown in the accompanyingdrawings, in which:

FIGURE l is a cross sectional view of a burner construction'of theinvention and having indicated diagrammatically therein premixing andtoroidal flow of products of combustion;

FIGURE 2 is a cross sectional view taken on the line 2-.2 of FIGURE l;

FIGURE 2a is a cross sectional view of a burner constructionillustrating a modified form of premixing charnber;

FIGURE 3 is a cross sectional view of a burner con structionillustrating `still another form of premixing chamber;

FIGURE 4 is a cross sectional View of a burner construction havingcoolant circulating means associated therewith;

FIGURE 5 is a graph illustrating stabilized burning curves; and

FIGURE 6 is still another cross sectional view of a burner constructionin which improved circulating means for reactants are provided.

The burner structures shown in FIGURES l to 3 inclusive, are intended toillustrate a means of carrying out the method of the invention in onesimple form. ln general, the invention method is initiated byintroducing into an elongated premixing space under pressure a flow ofliquid fuel such `as kerosene, oxygen and an inert gas such as nitrogenand causing the liquid fuel to become dispersed at temperatures :belowthat at which kerosene becomes a vapor. The liquid droplets occur invarying sizes and are substantially homogeneously, distributedthroughout the oxygen and nitrogen. It `should be observed that keroseneat temperatures of 100 F. and higher may occur in a mist or droplet formand will become a kerosene vapor at approximately 440 F.

The resulting mixture is conducted from the premixing space through anaperture into a combustion chamber which has a llame stabilizing surfacesurrounding the aperture. The flow of fuel droplets and oxidant throughthe aperture takes place at a relatively high velocity V1 and themixture decelerates to a velocity V2 in the relatively greater volume ofthe combustion chamber.

In the combustion chamber the mixture burns at superatmosphericpressureat a velocity of flame propagation which may be expressed as a velocityVp. The limit velocity of this flame propagation is a function of thequantity of nitrogen in the combustion chamber, and by regulating inputof fuel droplets in accordance with the ratio of oxygen to nitrogensupplied, and by controlling the flow of the total mixture, the velocityV1 is always maintained greater than the velocities V2 and Vp. VelocityV2 is always maintained less than Vp. With these requirements observedand a suitable combustion chamber size utilized the flame burnscontinuously without lbeing extinguished and a lowering of temperaturedependent upon the quantity of nitrogen employed is constantly realizedin the stream of products of combustion leaving the combustion chamber.It has been found that with combustion chamber diameters less than oneinch, it is exceedingly difficult if not impossible to sustain highspecific mass ilows. In the method of the invention good results havebeen obtained with burner diameters of from 2 to 4 inches in producingthe nitrogen cooled flame jet.

Considering these steps in relation to FIGURE l of the drawings, numeral2 denotes a tubular premixing chamber having a premixing space 4.Supported through one end of the member 2 is a fuel supply pipe 6 whichis connected to some suitable fuel supply such as a kerosene tank andpumping apparatus not shown in the drawings. The extremity of pipe 6 islocated in spaced relation to an inner surface 7 of the member 2 toprovide for flow of liquid fuel under pressure into the premixing space.

Also extending into the premixing chamber 2 is an oxygen supply conduit10 with control valve 10a and a nitrogen supply conduit 12 with controlvalve 12a. These members are also connected to respective oxygen andnitrogen tanks having `suitable valve means for supplying these gasesunder pressures wh-ich can be regulated in a conventional manner.

Attached to the premixing chamber 2 by threads 11 is a second tubularbody 14 which has a combustion chamber 16 therein. The combustionchamber preferably consists of a cylindrical member and when threadedover the premixing body 2 is closed at one end by the portion 7 of thepremixing chamber. Formed through the end wall 7 is an aperture Athrough which gases and fuel can pass at relatively high velocity V1into the combustion chamber 16 and decelerated to a relatively lowervelocity V2. At its opposite end the tubular body 14 is formed with latapered portion 18 which terminates in a llame jet outlet 20.

An important feature `of the :structure described is the combinationwith a premixing chamber of an oriced body having a relatively largeannular area 24 which extends around the fuel injection aperture A at arelatively abrupt angle thereto. This provides a flame stabilizingsurface against which products of combustion may be lf recirculated whenthe burner is operated in accordance with the method of the invention.

In producing a flame jet with the structure described the burner may bestarted by furnishing lliquid fuel through the member 6. Gxygen issupplied through the member 10 and fuel and oxygen are forced throughthe aperture A being ignited in the combustion chamber by some suitableigniting means of conventional nature commonly employed in llame jetoperation. Thereafter, a supp-ly of nitrogen may be introduced throughthe conduit 12 and the quantity of oxygen employed is substantiallyreduced.

In reducing the ratio of oxygen contained in the total mixture (whichresults from introducing oxygen with an inert gas `such as nitrogen, forexample as these gases occur in atmospheric air) the region of stableburning earlier referred to in the specification changes sharply as isillustrated in FIGURE 5 and the precent fuel and stream velocity must beregulated to avoid llame extinction.

Subject to these limiting conditions oxygen under a pressure of, forexample, 6 atmospheres and nitrogen in the form of atmospheric air undera pressure of p.s.i. gauge is expanded yat high velocity into thepremixing chamber with'the `result that fuel discharged through themember 6 is subjected to a high degree of turbulence in the premixingchamber and becomes broken up into a dispersion of liquid dropletssubstantially lhomogeneously dispersed in the oxygen and nitrogen. Thismixture after passing through the aperture A is decelerated to avelocity V2 which is less than V1 above-noted and the mixture burns inthe combustion chamber to produce products of combustion. A portion ofthe reactants sointroduced burns almost instantly and the resultingprod- Iucts of combustion are emitted from outlet 20 to form a flame jetwhose temperature is lowered by the nitrogen present.

In accordance vwith the invention another portion of the products ofcombustion including partially combusted coarse droplets are caused torecirculate in the manner illustrated by the curved arrows shown inFIGURE l in a toroidal path of travel. The recirculated portion of thellame is contained against the flame stabilizing surface 24 and guidedradially inwardly to contact with incoming portions of the combustiblemixture at aperture A so as to ignite continuously these portions.

It is found that this recirculation develops to a significant degreewhen an appreciable quantity of nitrogen is present in the combustionchamber and it is understood to be due to the fact that the nitrogenlimits the velocity of flame propagation. It is pointed Iout that therecirculated portion contains reactants as well as products ofcombustion. The fuel contained rin this recirculated portion iscomprised of both large and small droplets as Well as vapor. Thus thereis, in some instances, -a short interval of time in which burningdroplets may move into contact with incoming combustible mixture. Thetoroidal shape of the path of recirculating droplets has been visuallyobserved and appears substantially in the form shown in FIGURE 2 as atorus T.

An essential feature of the burner construction, therefore, is ytheprovision of a substantial annular surface area 24 surrounding theaperture A and toward which surface burn-ing droplets may berecirculated and guided inwardly towards the stream of incoming fuelmixture. In order for the recirculation of burning droplets to takeplace without the llame front actually flashing back into the premixingchamber, it is further essential that the velocity V1 of the incomingfuel mixture be greater than the velocity Vp of flame propagation, whileat the same time providing for the velocity Vp of flame propagation bemggreater than the velocity V2 of the reactants.

These relationships I have found may be maintained by regulating theratio of oxygen to nitrogen and by controlling the flow of total mixtureinto the combustion chamber. The controlling steps, it will be seen, aremade possible because of the action of the nitrogen in limiting thevelocity of llame propagation so that V1 can be maintained greater thanV2 and flashing back prevented.

As an instance of a typical burner operation to provide a cooled llamejet in accordance with the invention, the following values for afuel-air mixture are cited whereby the necessary regulation isaccomplished.

Compressed air at 90 p.s.i. gauge from an air compressor is metered by avalve to supply a flow of 354 standard cubic feet per minute to theburner. Fuel oil is delivered at 100 p.s.i. gauge to an atomizing nozzleat a ilow of 1.92 pounds per minute. A nozzle exit diameter of 1,250inches produces a chamber pressure of `32 p.s.i. gauge with a resultingllame jet of 3,650 ft./sec. at 2,530 F. under identical reactant flowconditions but with a 1.750 inch diameter nozzle, the chamber pressureis reduced to 8 p.s.i. gauge with a jet velocity of 2,300 ft./sec. at3,300 F. In each case the burner chamber measured 2,450 inches insidediameter by 15.5 inches long. Oritice A was 0.750 inch diameter.

In FIGURE 2a, I have illustrated a modified form of burner constructionin which'I provide a premi-Xing member 2' and combustion chamber member14', together with oxygen and nitrogen supply conduits 10 and 12 andcontrol valves 10b and 12b, and a liquid iluid injector 6. Theconstruction and operation of this form of burner is similar to those ofthe burner of FIGURES 1 and 2 with the exception of the mixing chamber 4which is constructed with a relatively `small elongated passageway 5formed in a tubular body 9. The passageway 5 communicates with anaperture A as shown. For some types of fuel a superior premixing of fueland oxidant may be realized and a better control of droplet sizeachieved with this structure.

In FIGURE 3, I have illustrated another form of burner in which evenbetter control of droplet formation and distribution in an oxidant maybe realized. In this arrangement a combustion chamber 14 of the typecorresponding to chamber 14 and 14 of FIGURES l and 2, has threaded toone end thereof a cylindrical housing 28. At the outer end of housing 28is a second cylindrical body 30 of a smaller diameter than member 28.Supported in the cylindrical body 30 are air conduits 32 and 34 withcontrol valves 32a and 34a which supply a flow of air under pressure tothe chamber space 36 and then into the chamber space 38 which is ofrelatively larger diameter. Turbulent air contained in the space isforced through orifices as 40 in a foraminated fuel distributing sleeve42 which is threaded into the orilced llame stabilizing shoulder 33. Afuel pipe 44 is connected to the opposite end of the sleeve 42 andprovides for a llow of fuel through the sleeve in a relativelyrestricted passageway which is constantly s-ubjected to turbulent jetsof air entering the opening 40. A very high degree of droplet dispersionin the oxidant gasses may be obtained with this arrangement and isparticularly effective with combustion chamber of relatively smalldiameter in the 2 to to 4 diameter range.

I may desire to operate the method of the invention with the use of acoolant for cooling the combustion chamber walls where a precise controlof combustion chamber temperature may be important. FIGURE 4 illustratesa premixing chamber with a burner capable of utilizing oxygen enrichmentand having water cooling. Air entering through a pipe 51 is controlledby valves 52a and Sla in members 49 and 49a passes from the annularvolume 52 through holes 54 contained in the fuel injector 53. F-uel isintroduced through the spray nozzle 50 and is mixed thoroughly with theair flow bythe turbulent action set up in the premixing chamber 55.Oxygen, as required to increase the `total oxygen content in the air, isconducted through a tube 56 and a passageway 57 to enter the combustionchamber 59. The restricting nozzle section 60 may or may not beutilized, depending on whether high exit velocity is required. With thisarrangement I combine special watercooling means as shown. Water entersa conduit 62 and passes along an annular `space 61 dened between the twoconcentrically arranged tubes 67 and 68. From the annular space water iscirculated out through an exit pipe 63. By controlling the flow ofcoolant through the passageway described, desirable control of thetemperature of the combustion chamber may be realized.

Another form of burner in which air cooling is utilized in flamedrilling a hole in a work body has been illustrated in FIGURE 6. In thisform of burner a premixing chamber 310 is furnished with compressed airfrom a conduit 312 and valve 3l2a and this air is tur'bulently mixedwith fuel injected lfrom a nozzle 314 and passed through a tubularmember 316 into the combustion chamber 318 of a burner 320.

The burner 320 is provided with a llame stabilizing surface 322 and isalso constructed with an outer cylindrical part 324 to dene an annularpassageway 326. A flame jet is produced by nitrogen cooled products ofcombustion in the manner already described and is emitted through arestricted outlet 328. In addition, there is provided a second airsupply system consisting of a separate air conduit 330 and valve 330ewhich supplies compressed air 4through passageways 332 into annularspace 326. This secondary air passes along the annular space 326,cooling burner wall surface and then a part of the air is dischargedthrough ports 340 and caused to circulate between the outer burner wall324 and a sur- Iturn of spalled material out of the hole.l

While I have shown preferred embodiments of burners of :the invention,it should be 'understood that other forms of burners and modifieddevices of the invention may -be resorted to within the scope of theappended claims.

I claim:

1. A burner apparatus for burning liquid fuel, oxygen and a quantity ofnitrogen at superatmospheric pressure and producing a nitrogen cooledllame jet, said apparatus including an enclosure body having anelongated mixing space for premixing oxygen, nitrogen and liquid @fueldroplets, means for introducing compressed oxygen, nitrogen and liquidfuel droplets to said mixing space in individually regulatablequantities, said enclosure body further having a relatively largercombustion chamber communicating with the premixing space, a llamestablizing wall constructed and arranged to separate the premixing spaceand the combustion chamber, said flame stabilizing wall being formedwith a fuel injecting passageway for conducting a fuel mixture from thepremixing space into the combustion chamber, said llame sta'blizing wallfurther presenting a flat annular flame stabilizing surface which islocated around and which extends abruptly away `from said fuel injectionpassageway, said combustion chamber having a predetermined size whichdefines a volume limited by the quantity of nitrogen relative to thequantity of oxygen and fuel droplets combusted therein whereby a rangeof stable burning above and below stoichiometric range is realized andrecirculation of flame portions may be induced against the said llamestabilizing surface in a toroidal path of llOw to promote continuousburning.

2. A burner construction according to claim 1 in which the premixingspace and the combustion chamber section include means for separatelyintroducing liquid fuel droplets dispersed in nitrogen and oxygen, acylindrical casing located around said combustion chamber section inspaced relation thereto to dene an annular passageway and means forintroducing a ow of coolant into and out of the said annular space.

3. A structure as defined in claim 1 in which the premixing spaceincludes a confined mixing area into which said compressed nitrogen,oxygen, and liquid fuel droplets may be introduced and a tubular memberextended through the confined space and being formed with openings foradmitting oxygen and, nitrogen and liquid fuel droplets in a turbulentmanner.

4. In a method of burning at superatmospheric pressure a mixture ofoxygen, nitrogen and a liquid fuel in a confined space to produce acooledflame jet, the steps which include introducing into a confinedmixing space a flow of liquid fuel and a flow of oxygen and nitrogen ingaseous form while controlling the ratio of oxygen and nitrogen suppliedand turbulently mixing the fiows to prod-ucc a dispersion ofheterogeneously sized fuel droplets in the said oxygen and nitrogen,maintaining the mix-v ture of fuel droplets, oxygen and nitrogen whilein the confined mixing space at a temperature below that at which theliquid fuel vaporizes, conducting said mixture from the confined mixingspace through an aperture into a combustion chamber of predeterminedsize at a high input velocity, decelerating the mixture to a loweredcombustion chamber velocity and simultaneously burning the mixture atsuperatmospheric pressure to provide nitrogen cooled products ofcombustion whose velocity of flame propagation is retarded by the saidnitrogen component, inducing in the combustion chamber a recirculationof some of the products of combustion at the lowered combustion chambervelocity noted and continuously forming a toroidal flame massconcentrically located around the said aperture in a position toconstantly ignite incoming portions of fresh fuel droplets and oxidantmixture and individually control-ling flow of fuel droplets, oxygen andnitrogen in relation to one another and as a function of the saidpredetermined combustion chamber size to maintain the said inputvelocity of the mixture entering the combustion chamber always greaterthan the said lowered combustion chamber velocity and to furthermaintain the lowered combustion velocity always less than the velocityof flame propagation whereby a range of reactants for stable burning isextended above and below stoichiometric range.

5. Method of burning at superatmospheric pressure in a confined space amixture of oxygen, a liquid fuel and a desired quantity `of nitrogen toproduce a high velocity flame jet in which the temperature of the ame isappreciably reduced by the nitrogen and the ratio of fuel and oxygen ismaintained within definite limits which are neither too rich nor toolean to support combustion in the presence of the said quantity ofnitrogen, said method including the steps of introducing into a confinedmixing space under pressure a flow of oxygen and nitrogen in gaseousform and a flow of liquid fuel held at a temperature below that at whichthe fuel vaporizes to produce a premix in which the liquid fuel isdispersed into heterogeneously sized fuel droplets in said oxygen andnitrogen, conducting the said premixed oxygen, nitrogen and fueldroplets from the mixing space at a relatively high input velocitythrough a flame stabilizing region into a combustion chamber of a sizewhich is predetermined and in which the mixture decelerates to a loweredcombustion chamber velocity, simultaneously burning the mixture in thecombustion chamber to provide products of combustion which extend fromend to end of the combustion chamber and whose velocitiy of flamepropagation is limited by the said nitrogen component, inducing arecirculation of the products of combustion in the chamber tocontinuously form a toroidal flame mass concentrically located aroundthe said aperture in a position to constantly ignite incoming portionsof the fuel droplets and oxidant mixture and continuously regulating thequantities of fuel droplets, oxygen and nitrogen supplied to valueswhich are related to one another and which are also a function of thesaid predetermined combustion chamber size thereby to maintain the saidhigh input velocity of the premix always greater than the said loweredcombustion chamber velocity and to further maintain the loweredcombustion chamber velocity always less than the velocity of fiamepropagation whereby a range of reactants for stable burning is extendedabove and below stoichiometric range.

6. A method according to claim 5 in which the combustion chamber is of asize not less than one inch in diameter.

7. A method according to claim 5 in which the size of thecombustionchamber occurs in a range of cornbustion chamber diameters of from oneinch up to approximately four inches.

References Cited by the Examiner UNITED STATES PATENTS 1,325,116 12/1919Sebille 15S- 117.5 2,367,119 l/l945 Hess 15S-27.4 2,628,817 2/1953Wyland 15S-27.4 X 2,725,929 12/1955 Massier` 175-14 X 2,861,900 11/1958Smith et al. 15S-27.4 2,882,017 4/1959 Napiorski 15S-27.4 X 2,896,9147/1959 Ryan 175--14 3,030,733 4/1962 Johnson 158-28 X 3,092,166 6/1963Shepherd 158-117.5 X

JAMES W. WESTHAVER, Primary Examiner.

MEYER PERLIN, FREDERICK L. MATTESON, IR.,

Examiners.

V. M. PERUZZI, M. L. BATES, Assistant Examiners.

1. A BURNER APPARATUS FOR BURNING LIQUID FUEL, OXYGEN AND A QUANTITY OFNITROGEN AT SUPERATMOSPHERIC PRESSURE AND PRODUCING A NITROGEN COOLEDFLAME JET, SAID APPARATUS INCLUDING AN ENCLOSURE BODY HAVING ANELONGATED MIXING SPACE FOR PREMIXING OXYGEN, NITROGEN AND LIQUID FUELDROPLETS, MEANS FOR INTRODUCING COMPRESSED OXYGEN, NITROGEN AND LIQUIDFUEL DROPLETS TO SAID MIXING SPACE IN INDIVIDUALLY REGULATABLEQUANTITIES, SAID ENCLOSURE BODY FURTHER HAVING A RELATIVELY LARGERCOMBUSTION CHAMBER COMMUNICATING WITH THE PREMIXING SPACE, A FLAMESTABILIZING WALL CONSTRUCTED AND ARRANGED TO SEPARATE THE PREMIXINGSPACE AND THE COMBUSTION CHAMBER, SAID FLAME STABILIZING WALL BEINGFORMED WITH A FUEL INJECTING PASSAGEWAY FOR CONDUCTING A FUEL MIXTUREFROM THE PREMIXING SPACE INTO THE COMBUSTION CHAMBER, SAID FLAMESTABILIZING WALL FURTHER PRESENTING A FLAT ANNULAR FLAME STABILIZINGSURFACE WHICH IS LOCATED AROUND AND WHICH EXTENDS ABRUPTLY AWAY FROMSAID FUEL INJECTION PASSAGEWAY, SAID COMBUSTION CHAMBER HAVING APREDETERMINED SIZE WHICH DEFINES A VOLUME LIMITED BY THE QUANTITY OFNITROGEN RELATIVE TO THE QUANTITY OF OXYGEN AND FUEL DROPLETS COMBUSTEDTHEREIN WHEREBY A RANGE OF STABLE BURNING ABOVE AND BELOW STOICHIOMETRICRANGE IS REALIZED AND RECIRCULATION OF FLAME PORTIONS MAY BE INDUCEDAGAINST THE SAID FLAME STABILIZING SURFACE IN A TOROIDAL PATH OF FLOW TOPROMOTE CONTINUOUS BURNING.